Electric lamp and method of making the same.



G. P. STEINMBTZ. ELECTRIC LAMP AND METHOD or MAKING THE SAME.

APPLICATION FILED SEPT. 28, 190B.

Patented Jan. 26, 1909.

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APPLICATION FILED SEPT. 28, 190B.

Patented Jan. 26, 1909.

2 SHEETS-SHEET 2.

IN YEN TUH. CHARLES 2? S'JZJZYME'TZ.

UNITED STATES PATENT OFFICE.

CHARLES P. STEINMETZ, OF SGHENEGTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

'- ELECTRIC LAMP AND METHOD MAKING THE SAME.

i No. 910,969.

Specification of Letters Patent.

' Patented ran. 26, 1909.

I Original application filed. November 17, 1902, Serial No. 131,650. Divided and this application filed. September 28,

To all whom it may concern: Be it known that I, CHARLES P. STEIN- ME'rz, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Electric Lamps and Methods of Making the Same, of which the following is a specification.

The present application is a division of one filed by me November 17, 1902, Serial No. 131,650. a

I have found that the operation of electric lamps of that type of which the so-called mercury arc lamp is the best known exam le is much improved if they are run at hig er temperatures than those which have heretofore been practiced.

If mercury be em loyed as the volatile electrode, the color 0 the light improves as the temperature of the lamp increases. Moreover if the lamp is run at a higher temperature other substances such as lithium, potassium, magnesium, sodium, and various combinations of these metals may be added to the mercury by which the quality of the light can be still further improved. In place of using mercury or substances containing mercury, other materials having a comparatively low boiling point may be emp oye'd to form the va orizing electrode of the lam If these su bstances are employed in t e va or arc lamp running at the temperatures w 'ch have heretofore been commonly employed, the advantages due to their light-giving power are only partially obtained as the temperature is not high enough to volatilize them in sufficient quant1t1es.

Another advantage, which results from the employment of high temperatures in lamps of this character, is due to the fact that with such temperatures, the drop in voltage between thelamp terminals necessary in orderthat the lamp may be used on ordinary circuits can be obtained with a tube which is considerably shorter than those heretofore employed. The limit to the temperature at which it has heretofore been possible to run these lamps has been given y the heat-resistin formin the walls 0% in whic the terminals of the lamp are placed. I have found that if the wall or walls of the exhausted chamber, or at least of that porpower of the glass tube the exhausted chamber Serial No. 455,110.

tion of it surrounding the light giving arc, are made out of fused quartz, the temperature-at which. the lamp can be operated is greatly increased, and that thereby the above noted advantages due to such 'an increase in temperature can be obtained[ Tubes formed of fused quartz will stand heating to a much higher temperature without softening than will glass tubes, moreover rapid and extreme changes of tern erature do not have the tendency to crack the tubes which exists with glass tubes under such conditions.

In the accompanying drawings I have illustrated several embodiments of my invention.

In the drawings Figure 1 is a sectional elevation showing one construction of lamp; Fig. 2 is a partial sectional elevation showing a slightly'modified construction; Fig. 3 is a sectional elevation showing a somewhat different construction of lamp ;.Fig. 4 is a diagram showing the relative proportion of the different materials composing the lamp tube shown in Fig. 3; Fig. 5 is a sectional elevation showing apparatus employed in the manufacture of lamp tube shown in Fig. 3; and Fig. 6 is a plan view showing the same apparatus. I g

In the construction showni Fig. 1, a light-transmitting tube 1 made out of fused quartz forms the inclosing chamber of my forms the other main electrode.

The tube 1 is provided .at its lower end with an ofi-shoot 4 and in this off-shoot 4 is laced another mass 5, similar to the mass 3, orming an auxiliary or startin electrode. The lower end of the tube 1 and t e off-shoot 4 are shaped to form comparatively small tapered necks 6, and on the outside of these tapered necks are fitted caps of metal 7. The outer surface of the necks 6 and the interior surface of the caps 7 may be ground to form air-tight joints. The metal caps are in electrical contact with the mercury and have suitable current-carrying leads connected to them. The metal out of which I form the caps 7 is a mixture of nickel with iron or steel, the amount of nickel in the composition being about 35% to 37%. I em loy this mixture as'its thermal coefficient ex' to the difliculty of making a sealed joint such as is em loyed with lass tubes due to the efiect on the metal of film very high temerature which it is necessary to employ to use the quartz. I have shown the caps 7 provided at their upper ends with a space 8 in which a quantlty of mercury may be placed. This forms a mercury seal which tends greatly to improvethe tightness of the joint made at this point. I

The solid electrode can be formed of a mass of iron or carbon and is carried by a tapered plug 9 of metal of the same composition as that employed to form the ca s 7. The tube is ground interiorly at 10 an the plug 9 is inserted to make a tight fit. Above the portion 10 the end of the tube may be flared to form a chamber 11 in which a uantityof mercury is placed to seal the oint. The terminal 2 may or may not be integral with the tapered plug 9. Preferably the terminal 2 and the plug 9 are connected by a portion 12 considerably smaller in diameter than the terminal 2 in order that the heat conducted from the terminal 2 to the plug 9 may be diminished. The tube 1 is exhausted in the same manner as has heretofore been employed in exhausting glass tubes. Atb13 I have indicated the fused off exhaust tu e. r

In Fig. 2 I have shown a slightly different method of closing the upper end of the tube. In this construction a cap 9, similar to the cap 7 shown at the lower end of Fig. 1, is employed at the upper end of the tube. The sohd terminal 2 is connected thereto by a slender portion 12 as in Fig. 1. The upper end of the quartz tube may be sha ed to receive a mercury seal, if desired. stead of forming the tube entirely of quartzand' forming metallic end connections as above described, the tube may "be made with its body portion of fused quartz and its end portions of some different substance into which metallic leading-in wires can be fused in the ordinary manner heretofore racticed in making tubes for lamps of this 0 aracter.

In Fig. 3 I have shown a lamp of this character similar in its general arrangement to the lam shown in Fig. 1, but in which the ort'ion o the lam tube 1' between .the es A A and B is formed of fused uartz, while the terminal portions beyond t e lines A A and B B respectively are formed of a material containingsilica, united with various other substances; for instance,

potassiumand calcium hydroxid may be added to the .fused quartz 'to make the com osition of the tube 1.-

cooled a shell 0 fused quartz formed surrom zero at "the lines A A and B B res ectively to an amount sufiicient to form a g ass into which a platinum wire can readily be sealed, as shown, and having practically the same. thermal coefiicient of expansion as platinum at the end. I

' In Fig. 4 I have shown a diagram illustrating the proportion of the materials in the In this dia am the 'ne D D is equal to the length 0 the tube 1 and the amount of quartz which is found in the tube' at any point along its length is proportional to the distance between the line CBAC and the line D D at the corresponding point. The amount of other materials employed to form the terminal portions of the tube are indicated by the distance between corres onding oints on the line CBAC and on t e line E AE. It will of course be understood that the quartz and other materials are intimately mlxed'and are not separated by any distinct 1 line of "cleavage as might appear from the diagram. With a tube as thus constructed, the mechanical resiliency of the tube'is sufficient to take u the diiference in the thermal ex ansion of t e tube at the lines A A and B respectively and the points where the terminal wires are sealed in.

In forming the lamp tubesabove described, the following method may be followed: A refractory. conductor such as'carbon may be embedded in a mass of quartz granules or silica in other finely divided states. On the passage of a heavy electric current through the conductor, heat is produced sufficient to fuse the quartz in the vicinity of the conductor, whereu on when the conductor is rounding the conductor.

In Figs. 5 and 6 I have illustrated an arrangement bywhich such tubes may be formed. In these drawings the carbonheating conductor 14-has substantially the shape which it is desired to give the inside of the tube. The conductor 14 is connected atits ends to heavy metallic conductors 14 which are mounted in the wall 15 of the furnace chamber. the lower part of the chamber 15 and surroun the conductor 14 is a mass of the materia which it is desired to fuse in ord'er to form a tube. At 16 is desired to form a tube like that in Fig. 3 134 the material surrounding different portions of the core will be different. 'Only that portion of the heating chamber between the lines A A and B B, which correspond in position with reference to the tube to the lines AA and B B of Fig. 3, will be filled with quartz alone. Portions between the lines A A, B B and the adjacent ends of the casing will be filled with a mixture containing other materials: that is, with the tube above described, the quartz will be mixed with potassium and calcium hydroxid and the mass of potassium and calcium hydroxid will be graduated in the space between the lines A" A and B B and the adjacent ends of the casing as indicated in Fig. 4. The rough tube-blank obtained in the heating chamber may have the carbon core burned out and be worked into a finished form by heating in the electric are or other source of great heat.

The operation of the lamp is as follows: At starting, the solid terminal 2 and .the vaporizing terminal are connected to one side of the supply circuit, while the main va 0- rizing terminal is connected to the other side of the line. If, now, the tube be agitated slightly so as to cause the metal forming the terminal 3 to contact with metal forming the terminal 5, an initial vaporization takes place and the vapor thus formed enables the current to pass from the terminal 3 to the terminal 2. After starting, the auxiliary terminal may be cut out if desired. The terminal 2 may have an extension 2 preferably formed of a carbon filament depending from it to a point slightly above the surface of the mercury 3 to assist in starting the are if desired.

If the substance employed to form a vaporizing compound is not fluid at ordinary temperatures, other means for starting the lamp may be employed, as, for example, those disclosed in British patent 5545 of 1903.

While I have illustrated and described the best form of my invention which is now known to me, I do not intend to be limited to the details of construction shown and deby Letters Patent of the United States, is,

1. As an article of manufacture, a tube having a body portion formed out of fused quartz, and end portions formed out of fused quartz combined with potassium.

2. As an article of manufacture, an integrally formed tube having a body portion formed of fused quartz, and end portions formed of a mixture of fused quartz with a substance which unites with quartz to form lass.

g 3. As an article .of manufacture, an integrally formed tube having a body portion formed of highly refractory material and an end portion of considerable extent and formed of less refractory material.

4. As an article of manufacture, an integrally formed tube, the body portion of which is formed out of fused quartz andthe end portions formed out of fused quartz combined with other substances, the proportion of the other substance increasing from the body of the tube to the end of the tube.

5. In a vapor arc lamp, an inclosing chamber having a body portion formed out of fused quartz and an end portion formed out of a different material.

6. in a vapor arc lamp, an inclosing chamber in the form of a tube having a body formed out of fused quartz, end portions formed out of a mixture of fused quartz and some substance which unites with itto form glass, and current carrying leads associated with said end portions.

In witness whereof, I have hereunto set my hand this 26th day of September, 1908.

CHARLES P. STEINMETZ.

Witnesses:

BENJAMIN B. HULL, MARGARET E. WOOLLEY. 

